feat(server): add TenantRegistry with per-tenant health tracking #1369

Job	Run time
Postgres conformance tests (Postgres 16)	1m 6s
Validate schemas are up-to-date	3m 41s
AdCP storyboard runner — v3 reference seller (translator)	1m 15s
Downstream import smoke (representative consumer symbols)	24s
AdCP storyboard runner — sales-proposal-mode (proposal_finalize)	1m 3s
AdCP storyboard runner — examples/seller_agent.py	1m 21s
Validate conventional commit format	9s
v3 reference seller — pytest (respx-mocked upstream)	39s
Test Python 3.12	3m 38s
Test Python 3.10	3m 45s
Test Python 3.11	3m 33s
AdCP storyboard runner — examples/multi_platform_seller (PlatformRouter)	1m 25s
Test Python 3.13	3m 37s
	25m 36s

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